(1) Field of the Invention
This invention relates to substrate treating apparatus for treating semiconductor wafers, glass substrates for liquid crystal displays and so on (hereinafter called simply substrates). More particularly, the invention relates to a technique for treating substrates as immersed in a treating solution stored in a treating tank.
(2) Description of the Related Art
Conventionally, this type of apparatus includes a treating tank for storing a treating solution, a holding mechanism movable into the treating tank while holding a plurality of substrates aligned in upstanding posture, and a rotating mechanism for rotating the holding mechanism about a virtual horizontal axis serving as the center of rotation extending in the direction of alignment of the substrates (see Japanese Unexamined Patent Publication No. 2003-59879, for example).
With this apparatus, a plurality of substrates are immersed along with the holding mechanism in the treating solution stored in the treating tank, and are treated for a predetermined time while being rotated about the virtual horizontal axis by the rotating mechanism. The apparatus is intended to treat the plurality of substrates uniformly by rotating the substrates for causing the treating solution to contact the entire surfaces of the substrates.
The conventional apparatus noted above has the following drawbacks.
With the conventional apparatus, since the plurality of substrates are rotated about a virtual horizontal axis serving as the center of rotation extending in the direction of alignment of the substrates, central portions of the substrates make very little movement although peripheral portions of the substrates move through extensive ranges. Consequently, the degree of contact with the treating solution differs greatly between the central portions and peripheral portions of the substrates. This poses a problem that the substrates cannot be treated uniformly over the entire surfaces thereof.
Since the central portions of the substrates are treated more slowly than the peripheral portions, the treatment is performed in a way adjusted to the central portions. This results in a drawback of requiring a long treating time.